PROJECT SUMMARY This is a resubmission for a K23 award for Quinn Pack, MD, MSc, a board-certified cardiologist and Assistant Professor at the Tufts University School of Medicine (TUSM). Dr. Pack is based in the Center for Quality of Care Research (CQCR) at Baystate Medical Center (BMC) in Springfield, Massachusetts. Dr. Pack's focus is on increasing participation rates in cardiac rehabilitation (CR) for eligible patients after an acute cardiac hospitalization. His long-term goal is to become an independent cardiovascular implementation physician-scientist. His immediate goals are to obtain a mentored research grant, successfully complete his specific aims, and obtain additional training in dissemination and implementation from the University of Massachusetts Medical School (UMMS). His prior training as a cardiologist and preventive cardiologist, as well as his Master's Degree and Tufts KL2 award, will help him to accomplish these goals. Dr. Pack has assembled a mentorship team with expertise in the proposed work and in helping junior faculty transition to independence. His Primary Mentor is Dr. Peter Lindenauer, a nationally recognized expert in the field of comparative effectiveness research and implementation science. His Co-Mentors include Dr. Phillip Ades (CR expert), Dr. Kathleen Mazor (psychometrician), and Dr. Penelope Pekow (biostatistician). Dr. Pack will have full access to the resources of BMC, TUSM, and UMMS. The CQCR (directed by Dr. Lindenauer) will provide mentoring, biostatistical, and administrative support as well as a peer group of junior faculty with similar interests. The research proposal aims to answer the question: ?What are the factors and strategies that enable hospitals to achieve high risk-adjusted outpatient CR participation rates?? Despite powerful health benefits and strong society guideline recommendations for patients to attend CR after an acute cardiac hospitalization, nationally, as few as 20% of patients ever participate in CR. Because the vast majority of clinical events that qualify a patient for CR result in hospitalization, a logical place to encourage CR participation is during the patient's hospitalization. However, little is known about how hospital processes of care influence CR participation after hospital discharge. In Aim 1, using data from hospitalized Medicare beneficiaries, we will compute hospital-specific risk-standardized rates of CR to evaluate the role that hospitals play in facilitating CR participation. In the second Aim, we will perform a national survey of hospitals to identify the contextual factors and strategies associated with higher risk-standardized rates of CR participation. In Aim 3, we will use qualitative methods at high performing hospitals to explore the strategies and implementation factors that help these hospitals effectively promote CR participation. These projects will generate the knowledge and data needed for a future R01, in which we plan to conduct a randomized controlled trial to test a multifaceted intervention in order to increase rates of participation in CR following hospital discharge.